1. Field of the Invention
The present invention relates to an apparatus for rubbing an alignment layer, and particularly, to an apparatus for rubbing an alignment layer of a Liquid Crystal Display (LCD) device that is capable of uniformly rubbing an alignment layer by minimizing an affect due to a force of a rubbing roll that has an increased size and weight.
2. Discussion of Related Art
As various portable electric devices such as mobile phones, personal digital assistants (PDA), notebook computers, etc., continue to be developed, various types of flat panel display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum florescent displays (VFDs), having a compact construction, light weight, and low power-consumption also continue to be developed. Due to the ease with which they are driven and to their superior ability to display images, LCDs are extensively used in these electric devices.
The LCD device is a transmissive type display device for displaying images by adjusting an amount of light transmitted through a liquid crystal layer according to an alignment direction of liquid crystal molecules. Hence, an alignment process must be performed for the LCD device to provide each liquid crystal molecule with a uniform direction. In general, many methods are known to produce an alignment layer. An alignment method using a rubbing operation is currently used most frequently. The rubbing alignment method first forms an alignment layer on a substrate and then rubs the alignment layer by use of a rubbing cloth to form uniform microgrooves on a surface of the alignment layer. The alignment layer having the microgrooves on its surface provides each liquid crystal molecule with an alignment controlling force, thereby constantly aligning the liquid crystal molecules over the entire surface of the alignment layer in a desired direction.
However, the alignment method using rubbing may cause the following problems. The rubbing process may include a rubbing cloth that is wound on a rubbing roll and then is placed in contact with the rubbing roll while the rubbing roll is rotated and moved in one direction. Meanwhile, the LCD device is being employed in electric devices such as TV sets as well as portable electric devices recently and accordingly, the size of the LCD device is greatly increasing (furthermore, the mother substrate for fabricating LCD panels is much greater in size) that results in an increase of the width and weight of the rubbing roll used to perform the alignment process for a large LCD device.
In the meantime, the alignment controlling force or a surface fixing force of the alignment layer that is rubbed by the rubbing roll is determined by the microgrooves formed in the alignment layer, and the depth of the microgroove is different based upon a pressure of the rubbing roll applied to the alignment layer. However, as the width and weight of the rubbing roll increases, it is difficult to uniformly maintain the pressure applied to the mother substrate, that results in the fabrication of a defective LCD device by defectively rubbing the alignment layer.